The present invention relates to a transmitter of a tire condition monitoring apparatus and a method for manufacturing a transmitter of a tire condition monitoring apparatus.
A wireless tire condition monitoring apparatus has been proposed in the prior art to enable a driver to check the condition of the vehicles tires from the passenger compartment. Such a monitoring apparatus includes a transmitter, which is arranged in each tire and attached to the associated wheel, and a receiver, which is arranged on the body of the vehicle. Each transmitter detects the condition of the associated tire, that is, the interior air pressure of the tire and the interior temperature of the tire. The transmitter then sends a signal, which indicates the detected tire condition, to the receiver by means of wireless transmission.
FIGS. 5 and 6 show a prior art transmitter 1, which is described in Japanese Laid-Open Patent Publication No. 2000-25430. The transmitter 1 includes a valve stem 3, which incorporates a valve core 2, and a resin casing 4. The basal end of the valve stem 3 is formed integrally with the casing 4 when the casing 4 is formed. The casing 4 has an air conduit 12, which is connected with an internal air passage that extends through the valve stem 3. When filling the tire with air, the air enters the tire from the valve core 2 through the internal air passage of the valve stem 3 and the air conduit 12.
The casing 4 accommodates an electric circuit unit 5 and a battery 8, which supplies the electric circuit unit 5 with power. A pair of conductive plates 13 connect the battery 8 to the electric circuit unit 5. The electric circuit unit 5 includes a circuit substrate 6 and electric devices 14, such as a pressure sensor and a signal processor, which are connected to the circuit substrate 6. The electric devices 14 are shown schematically in FIG. 6. Three bosses 7 are formed in the casing 4. The circuit substrate 6 has holes corresponding to the bosses 7. The bosses 7 are inserted into the holes and heated. This melts the ends of the bosses 7 and fixes the electric circuit unit 5 in the casing 4. The casing 4 has an opening, which is closed by a cover 10.
When assembling the transmitter 1, the electric circuit unit 5 and the battery 8 are first arranged at a predetermined position in the casing 4, and the electric circuit unit 5 is fixed to the bosses 7. Then, the casing 4 is charged with a potting agent 9. This envelops the electric circuit unit 5 and the battery 8 in the potting agent 9. The potting agent 9 protects the electric circuit unit 5 and the battery 8 from moisture. Finally, the opening of the casing 4 is sealed by the cover 10. An aperture 11 extends through the cover 10 to communicate the interior pressure of the tire to the pressure sensor of the electric circuit unit 5.
As described above, to manufacture the transmitter 1, the electric circuit unit 5 and the battery 8 are first arranged in the casing 4, the electric circuit unit 5 is then fixed to the bosses 7, the casing 4 is charged with the potting agent 9, and the cover 10 is finally attached to the casing 4. Accordingly, many operations are required to manufacture the transmitter 1. Further, since the bosses 7 must be provided in the casing 4 to fix the electric circuit unit 5, the structure of the casing 4 is complicated. This makes it difficult to reduce the size of the transmitter 1. In addition, equipment for charging the potting agent 9 is necessary, and time is required for the potting agent 9 to harden. This makes the manufacturing of the transmitter 1 burdensome and increases manufacturing costs.
It is an object to provide a transmitter of a tire condition monitoring apparatus that has a superior moisture resistant characteristic, enables reduction in size, and facilitates manufacturing, and a method for manufacturing such transmitter.
To achieve the above object, the present invention provides a transmitter of an apparatus for monitoring a condition of a vehicle tire. The transmitter includes a casing formed from resin. An electric circuit unit is arranged in the casing to detect the condition of the tire and generate a signal corresponding to the condition of the tire. A battery is arranged in the casing to supply the electric circuit unit with power. The casing is insert molded to embed the electric circuit unit and the battery in the resin forming the casing.
A further perspective of the present invention is a method for manufacturing a transmitter of an apparatus for monitoring a condition of a vehicle tire. The method includes arranging an electric circuit unit, which detects the condition of the tire and generates a signal in accordance with the detected tire condition, and a battery, which supplies the electric circuit unit with power, in a mold. The method also includes insert molding the casing by charging the mold with molten resin to envelop the electric circuit unit and the battery in the resin.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.